The field of cancer modeling in the mouse has come a long way in the last two decades, and the pace of change is accelerating. With the recent commitments from the NIH and NCI to improve genomic tools for the mouse and to accelerate the sequencing of the mouse genome, the timing is right to scale-up cancer genetics in the mouse: with time, all major human tumor types should have one or more associated mouse models that accurately reflect the genetic and histopathological progression of the disease. The development of these mouse models requires the expert and efficient generation and analysis of genetically engineered mouse strains, as well as the generation and analysis of reagents derived from these animals. The general aim of the Core Facility CF3. Di Cristofano: Animal Models is to provide a facility in which this complex set of tasks will be optimized for 1) expert design and production; 2) efficiency; 3) cost reduction, with the following specific aims: 1) The Core Facility will generate and make available to SPORE investigators transgenic and knockout/knockin mouse strains of common interest; 2) it will assist individual components of the SPORE in the design and generation of targeting constructs as well as in the generation and characterization of the derived mouse strains; 3) it will serve as a centralized repository and breeding service for mouse strains of general use among SPORE investigators; 4) it will provide SPORE laboratories with dissected tissues, DNA, RNA and proteins from the various mouse mutants utilized by the investigators.